The present invention relates to an emergency towing system for shipping vessels.
Shipping accidents have lead to stricter international regulations. International rules have recently come into effect which require an emergency towing connection onboard various types of ships. A towing system should be fitted to the ship which would give a tugboat the possibility of assisting an out of control vessel in an emergency.
In practice, a first connection is often brought about by shooting a light line across from the tugboat to the ship to be towed. Onboard the ship which is to be towed, this is caught by people or by an automatic mooring system. A second possibility for making the first connection is to throw a buoy overboard with a connecting line from the ship that is to be towed. The tugboat then travels to this buoy and fishes both the buoy and the connecting line out of the water.
As soon as the first connection has been established, the light line is fastened to a winch on the tugboat and is used to bring a heavier cable across from the tugboat to the vessel to be towed. This process is continued until the actual towline has been brought across. After making the connection, the tugboat can tow the vessel.
So as not to be dependent on a winch on the ship to be towed, a return guide, such as a xe2x80x98roller pedestalxe2x80x99, is often fitted onboard this ship. The light cable can be laid around the roller and the free end can be brought over to the tugboat. In an emergency, however, it is difficult to get this cable to the tugboat. As soon as the light cable is back on the tugboat, the winch in the tugboat can be used to bring the heavier cable over, using the light cable via the roller.
In both cases, human intervention is needed on the ship to be towed, but this is not always possible in emergencies and in bad weather.
A number of proposals have been made to solve these problems. A first proposal is the permanent fitting of a heavy towline onboard the ship to be towed. The light connecting line can be directly coupled onto this and can bring the heavy towline over to the tugboat. This proposal means the permanent fitting of a large towline onboard the ship, with considerable cost, storage space and maintenance.
A second proposal is the fitting of a chain with a hook-system as described in WO 9711876. This system offers the possibility of still making a towing connection, without a towline being onboard the vessel to be towed. Here, a closed ring-cable is secured through the end link of the chain, by which the chain is pulled overboard. A special hook is also brought over to the tugboat. The tugboat attaches the towing line to this hook and pulls the hook via this ring-cable back to the ship to be towed, where the hook hooks into the chain. This system has a number of disadvantages, including:
1. Limited reliability of functioning due to the turning of both the chain and the messenger line, and the chance of a break during the peak load of the hooking in, and
2. The large load on the messenger line during the pulling around and hooking in of the hook. This system also consists of a number of parts which lie on the vessel""s deck in all weather and, in doing so, require maintenance and repairs.
The aim of the present invention is to provide an improved device which does not have the disadvantages mentioned above, that is, reduction of costs and maintenance and an increase in the reliability in emergencies and bad weather and without human presence on the vessel to be towed.
This aim is realized in an emergency towing system for shipping vessels, which comprises a return guide, fitted to the vessel to be towed, around which a closed ring-cable is fitted, wherein the ring-cable comprises a coupling-member which, when the ring-cable is heaved around, establishes contact with a contra-coupling-member on the vessel to be towed.
The return guide can comprise all constructions known in the state of the art to return a cable with minimum resistance, such as a roller. It should also be understood that a rounded object with a smooth surface can also be used in place of a roller.
The ring-cable can be connected to the light line of the tugboat; this can be done in any way known in the state of the art, both manually and automatically. The tugboat can then pull this closed ring towards itself.
By providing this ring-cable with a coupling-member, the heavier towline can be pulled around to the vessel to be towed and the coupling-member can hook into the contra-coupling-member onboard the vessel to be towed.
The coupling mechanism can comprise any of the constructions known in the art. According to an advantageous embodiment, the coupling-member is realized as a pin in the length of the ring-cable, whereby the connection between the pin and the cable is smooth. In this way, the pin can be pulled towards the ship to be towed without hooking onto anything. The contra-coupling-member in this embodiment is implemented as a tube-shaped opening with rounded edges. The closed ring-cable goes through the contra-coupling-member and, by pulling on the other part of the ring-cable, the connecting pin is easily pulled into the opening of the contra-coupling-member, guided by the rounded edges. The connection is made when the pin is pulled into the contra-coupling-member; for this purpose, the pin is provided with a countersunk edge and the contra-coupling-member has sprung projections on the inside. When the pin is pulled in, the projections are pushed apart by the shape of the pin and then move towards each other again as soon as the countersunk edge of the pin is reached. The pin is caught behind the projections and, in this way, the connection is realized. By implementing the pin so that it is rotationally symmetrical, the connection is no longer dependent on the correct turning of the connecting lines.
By this implementation, a reliable system is realized which also functions in emergencies and in bad weather.
By protecting both the return guides and the closed ring-cable from dirt and corrosion, the reliability is increased and the maintenance costs decrease.
According to an advantageous embodiment, both cables of the ring-cable are independently lead outside through openings in the ships outer shell, whereby one of the two openings is used for the contra-coupling-member and the other as the xe2x80x98pull throughxe2x80x99 opening. This stops the two connecting lines from hindering each other in one opening, both during the pulling around and the hooking-in of the pin.
According to a further advantageous embodiment, the closed ring-cable is stored in a separate box, wherein only the two ends protrude and are connected to the coupling-member via the contra-coupling-member and around the roller. This embodiment makes it possible, during the installation and maintenance, to handle the whole cable in the box as one part. The cable can first be stowed away in the box in a controlled manner.
To guarantee the reliable paying out of the cable, the cable should be stored in zigzag layers in the box. As a result of the zigzag structure, the cable does not rotate during paying out, preventing the cable from getting tangled and from hindering the functioning of the system.
As both ends of the ring-cable should feed out simultaneously, the ring-cable should either be installed in two separate boxes or a double cable together in a zigzag structure in one box. Practical tests show that the paying out from two separate boxes is more reliable and requires less effort.